where \(Q^{\prime }\)  is the clarifying question generated by the QCM model parameterized by \(\theta \) , and \(\mathbb {U}(Q^{\prime },Q)\)  is a utility function that measures how much the clarifying question \(Q^{\prime }\)  clarifies the information need of user when submitting the query \(Q\) .
Since the utility function is often not differentiable [1]}, [2]}, the mixed incremental cross-entropy REINFORCE algorithm (MIXER) [3]} is used for training the QCM model.
